Recent years have seen the development of a reflective liquid crystal display device referred to as a silicon-chip-based liquid crystal device for use as a head-mounted display or a projection display.
This type of reflective liquid crystal display device displays an image by shining light from a light source onto a liquid crystal panel and by projecting the reflected light from the liquid crystal panel onto a screen.
A unit constructed by forming as a silicon chip a semiconductor device for driving a liquid crystal panel and by mounting the liquid crystal panel on the semiconductor device is referred to as, for example, an LCOS (Liquid Crystal On Silicon) unit.
FIG. 1 is a diagram illustrating an LCOS unit according to the prior art. The LCOS unit 130 includes a liquid crystal panel 120 and a semiconductor device 110 as a silicon chip for driving the liquid crystal panel 120.
The semiconductor device 110 is formed on a silicon substrate 111, and includes a device layer 112 which contains circuit elements such as transistors T. The semiconductor device 110 further includes reflective electrode layers 115 each of whose electric potential is controlled by a signal from the device layer 112, and a bonding pad 114 which is used for supplying power to the device layer 112 as well as for transferring signals to and from an external circuit.
The reflective electrode layers 115 are arranged in a two-dimensional matrix array. A desired image is displayed by controlling the electric potential of each reflective electrode layer 115 and hence controlling the orientation of the liquid crystal in the liquid crystal panel 120.
In the example illustrated in FIG. 1, the reflective electrode layers 115 and the bonding pad 114 are disposed in the uppermost layer of the semiconductor device 110, and have the same thickness because they are formed simultaneously in the same process step by etching the same conductive layer.
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